Biometric recognition is a technology for biometrics authentication (or realistic authentication) by body measurements and calculations. The body measurements and calculations are related to biological characteristics, including fingerprint, palm print, veins, iris, retina and face. Nowadays, biometric recognition has been applied to many fields which require information privacy and personal safety, such as digital assistant, smart phone, desktop, debit card, digital wallet and customs authority.
A wide use of biometric recognition includes fingerprint recognition and finger vein recognition. In a conventional device for fingerprint recognition or finger vein recognition, in order to converge light from the finger onto the sensors, an optical system inside the device should satisfy thin lens formula (1/f=1/u+1/v, wherein f is a focal length of the lens, u is a distance from an object to the lens, and v is a distance from the lens to an image). A focal length of a lens satisfying thin lens formula leads to large size of the device so that it is unfavorable to apply this device on portable electronic devices. If the lens is removed, light received by the sensors is insufficient; also, light reflected by single biological characteristic, such as fingerprint or vein, is divergent toward multiple directions so that it may be received by multiple sensors, thereby outputting an image with low resolution to influence the accuracy of recognition. A useful way is to form a light passing part featuring high aspect ratio (more than 10) for preventing light divergence, thereby achieving point-to-point imaging. However, small size of hole for light passing on a light shielding layer lead to insufficient amount of light reaching the sensors; or, large size of hole for light passing leads to a demand of large thickness of the light shielding layer since high aspect ratio should be satisfied, thereby increasing both the size of device and manufacturing difficulty.